ITEMS FROM ARGENTINA

CÓRDOBA NATIONAL UNIVERSITY

College of Agriculture, P.O. Box 509, 5000 Córdoba, Argentina.

Evaluation of the effect of two cycles of recurrent selection for yield on breadmaking quality in wheat for the Argentine central semiarid region.

Z.A. Gaido, M.E. Dubois, G.A. Manera, and R.H. Maich.

Under a semiarid environmental condition of wheat cultivation, the basic plant breeder's purpose is to increase grain yield. Moreover, in bread wheat, it is necessary to determine the effect of this process on grain quality, an aspect related to the commercialization and industrialization of this cereal. The objective of this work was to study the effect of a recurrent selection scheme for grain yield on breadmaking quality in bread wheat cultivated under semiarid conditions in Argentina. Breadmaking quality was measured through protein content, gluten and mixograms. During 3 years of evaluation of the effect of two cycles of recurrent selection, significant progress for grain yield was observed without any influence on breadmaking quality. The breadmaking index obtained for the cycles analyzed showed high protein contents, adequate gluten, and very satisfactory mixograms. The results showed that the recurrent selection process was appropriate to increase grain yield in bread wheat without affecting grain quality.

Protein content and yield evaluation of wheat lines adapted to the Argentina central semiarid region.

G.A. Manera, Z.A. Gaido, R.H. Maich, and M.E. Dubois.

Plant breeding programs have not been able to maintain the quality of Argentine wheat, so the market transformation involves its quality improvement. A strategy would be to develop superior quality wheat varieties. The protein content and grain yield of the International Maize and Wheat Improvement Center wheat lines were evaluated , to consider the possibility of introducing the elite germplasm material at the time of the implementation of the wheat improvement program for the Argentina central semiarid region. These were compared with national varieties and local experimental lines obtained at Facultad de Ciencias Agropecuarias, Universidad Nacional de Córdoba. The experimental evidence suggested that CIMMYT lines stood out because of their high protein content, although local lines presented the largest protein yields. In this regard, CIMMYT lines may represent a good source of genetic variability to increase the protein content of materials developed for areas where an increase is needed.

Seed aspect changes related to population improvement.

I. Arguello, R.H. Maich, and R. Rolando.

During 1996, a yield trial was conducted with the objective to measure the genetic gain for grain yield after three cycles of recurrent selection (R.Maich AWN 43:46). Simultaneously, a sample of 50 seeds was taken from each experimental unit. Length, width, thickness, and weight of the seeds were measured. For all the characters analyzed significant differences between cycles were observed. The nean values for the more evolved population (C3) were lower than those for the less evolved population (C0). Decreases in dimensions and weight of the seed were observed at the end of the third cycle of recurrent selection.

Increased probability of superior recombinant lines obtained through a recurrent selection program.

R.H. Maich.

Previous results (R.Maich AWN 43:46) showed the difficulty of demonstrating significant progress in a plant breeding program developed through a cyclical process of selection and recombination. However, descriptive interpretation of the data furnish the possibility to prove one of the major paradigms of recurrent selection: 'the more evolved cycle of selection has a higher probability of giving superior recombinant lines'. During 1997, two grain yield trials were performed in order to measure the genetic progress. In one of them, the objective was to compare three cycles of recurrent selection (C0, C1, C2, and C3), and four cycles in the another one (C0, C1, C2, C3, and C4). Compared to the best check cultivar, 11 of 14 families with superior grain yields were originated from C2 and C3 cycles, and nine of 13 came from C3 and C4 germplasm when four cycles were evaluated. However, our experience demonstrates that at least a 3-year trial is needed to obtain reliable results from this recurrent selection program conducted under semiarid environmental conditions of cultivation.

Variation of the gene frequencies of Glu 1 loci due to a cyclical plant breeding program.

A. Ordoñez, R.H. Maich, M. Mestrallet, S. DeFilpo, and D. Manero de Zumelzú.

The baking properties of wheat are influenced by the presence of proteins in the kernel endosperm. Gliandins and glutenins are the predominant proteins in the endosperm. Glutenins are known to contribute significantly to protein quality, playing an important role in the bread-making processes. Glutenins comprise two subunits: HMW and LMW. The HMW-glutenin subunits are coded by the complex Glu 1 loci present on the long arm of the homoeologous group 1 chromosomes. On the other hand, selecting and crossing cyclically superior materials are possible to eliminate or fix those genetic determinants responsible for a character subject to genetic improvement.

With the objective of evaluating three cycles of recurrent selection for grain yield in bread wheat and to measure its effects on Glu1 loci gene frequencies, a sample of 60 seeds from each one of the selection cycles analyzed (initial, 1*, 2* y 3*) was characterized according to the banding pattern of HMW-glutenin subunits, determined by SDS­PAGE. Our results showed that, for two of three loci analyzed (GluA1 and GluB1), the frequencies did not change in respect to the original population; however the 2+12 allele of GluD1 loci, qualitatively inferior to 5+10 allele, was eliminated. Probably the loss of 2+12 was due to genetic drift effects.

Flag leaf width changes related to a microevolution process.

S.P. Gil, M.M. Cerana, and R.H. Maich.

Continuing work we have been doing since 1995, we studied changes of flag leaf morphological characters (length, width, and area). The bread wheat plants were sown in an experimental field placed in Ferreyra (Córdoba, Argentina) at 31o29' lat. S and 64o00'long W, during 2 consecutive years (1996­97). A completely random block design with two replications was used. Five flag leaves from each experimental units were analyzed. Significant differences between mean values corresponding to the width were found when the 12 families originated from C0 (the initial population) were compared to the another group of 12 families selected from the more evolved cycle (C3). A 5.4 % flag leaf width increase was observed when three cycles of recurrent selection were evaluated (P < 0.05).

Soft wheat in the Argentinean market.

Carlota Güino.

Argentina does not produce soft wheat and also has discouraged its production. Today, signals from domestic and international markets indicate that reversing this situation would be a benefit.

Soft wheat cultivars generally have higher yield per unit area, lower protein content, and less gluten strength than other type of wheat. Soft wheat flour is best used for making biscuits, cookies, crackers, other crumb products, and flat breads.

Descriptive market research aimed at supporting or rejecting favorable stands for the production of soft wheat and its commercial standards in Argentina was developed. The conclusions favor including soft wheat among the Argentine supply, and point out the necessity of coördinating efforts to reduce costs. The introductory stages will be particularly important, because they will define the effort and time needed for the acceptance of soft wheats in the market.

Publications.

Dubois ME, Gaido ZA, Manera GA, and Maich RH. 1998. Evaluación del efecto de dos ciclos de selección recurrente por rendimiento en semilla sobre la calidad panadera en trigos (Triticum aestivum L.) aptos para la región semiárida del centro de Argentina. Phyton (In press).

Dubois ME, Gaido ZA, Maich RH, and Manera GA. 1996. Contenido proteico en relación con el rendimiento de l'neas de trigo (Triticum aestivum L.) adaptadas a la región semiárida central de la Argentina. Agriscientia XIII:71-74.

Gaido ZA, Manera GA, and Dubois ME. 1996. Influencia de la selección por proté nas en generaciones tempranas sobre el rendimiento y la calidad en trigo (Triticum aestivum L.). Phyton 59(1/2):95-101.

Manero de Zumelzú D, Maich R, and Ordóñez A. 1997. Variación de las frecuencias del alelo 5+10 en trigo (Triticum aestivum L.) y su relación con la mejora de la calidad. La Alimentación Latinoamericana 217:60-62.

Cerana MM, Gil SP, Pascualides AL, Tablada EM, and Gonzalez LA. 1996. Epidermis foliar de trigo (Triticum aestivum L.) en relación al genotipo y al espaciamiento entre surcos. Agriscientia XIII:59-63.

INSTITUTE OF BIOLOGICAL RESOURCES - INTA

Las Cabañas y Los Reseros s/n, (1712) Villa Udaondo, Castelar, Pcia. de Buenos Aires, Argentina.

Biotechnology Institute - CICV - INTA.

CC 77, 1708 Moron, Castelar, Argentina.

SSR markers as a tool for identification of wheat cultivars with property in Argentina.

M.M. Manifesto, A.R. Schlatter, M. Echaide, H.E. Hopp 1, and J. Dubcovsky 2.

1 Faculty of Sciences, University of Buenos Aires, Buenos Aires; and 2 the University of California, Davis.

In order to test the utility of the SSR markers as a tool for identification of the Argentine wheat cultivars with property listed in the National Seed Register, we estimated the degree of polymorphism and genetic variability present at important microsatellite loci.

We analyzed 105 Argentine cultivars of bread wheat with four microsatellites located on different chromosomes:

1. LMW-glutenin SSR located in the locus Glu-A3 on the short arm of chromosome 1A,

2. omega-gliadins SSR on locus Gli-B1 on the short arm of chromosome 1B,

3. WMS-46 SSR on the short arm of chromosome 7B, and

4. Xcnl-5 SSR on chromosome 1A.

These four SSR loci indicated the presence of 39 different alleles. The number of alleles varied from 5­11 per locus, with an average of six per locus. The large number of alleles and their relative frequency resulted in high values of polymorphism information content (PIC) in three of four of the SSR loci tested, suggesting that they may serve as efficient descriptors of true-to-type identity.

The observed PICs were: PIC (LMW-glu) 0.82, PIC (omega-gli) 0.88, PIC (WMS-46) 0.70, and PIC (xcnl-5) 0.40. The high polymorphism level and, more specifically, the high polyallelism level indicates that microsatellites are the genetic markers of choice for varietal identification, particularly in species with low levels of genetic variability, as is the case for wheat.

Institute of Climate and Water - INTA - CIRN.

CC 25, (1712) Castelar, Buenos Aires, Argentina.

Prediction of the severity of Puccinia recondita f. sp. tritici infections.

R.C. Moschini and B.A. Pérez.

Leaf rust severity on bread wheat cultivars at Pergamino for the period from 1972­90 were used to identify, during early phenological stages, the best associated genetic and environmental predictors of disease severity. For June­July leaf rust epidemics, the equation PS % = 4.42 + 0.61 DD12 + 0.57 DRH70 ­ 30.01 RI explained 88 % of the disease severity variation, with DD12 [degree-day accumulation of base daily mean temperature (MT) > 12°C and relative humidity (RH) > 49 %; if MT > 18°C], MT = 18°C, and DRH70 (days with RH > 70 % and precipitation < 0.2 mm) monitored from 16 August until 475 degree-days were accumulated. The resistance index (RI) was the proportion of resistant wheat cultivars sown each year. General linear models were fit to the leaf rust severity data discriminated according to the infection type of the cultivars. The disease severity predicted by the models showed only slight differences from those observed locally (1994­96) and at other locations (1991). For late infections (August), the predicted value of meteorological variables decreased, whereas that of RI, being selected from the equation PS % = 16.64 + 0.46 DD11 ­ 40.38 RI, increased. The variable DD11 (DD12 with a base mean temperature of 11°C and an RH threshold of 50 %) was monitored from 28 August until 460 degree-days were accumulated.

The predictive models developed here are empirical and based on the analysis of historical series of disease severity, cultivar resistance score, and weather data. The results suggest that maximum leaf rust severity predictions can be made for June­July epidemics by monitoring the thermal variables (DD12, DDMAXT) and hydric conditions (DRH70) from mid-August to September. The models developed show the usefulness of predicting years with low, moderate, or high levels of leaf rust severity for locations far away from Pergamino. Early leaf rust epidemics responsible for the greatest wheat yield losses could be associated with, and predicted by, the environmental factors identified in this study, especially for wheat cultivars planted in June and July.

References.

Burleigh JR, Eversmeyer MG, and Roelfs AP. 1972. Phytopath 62:947-953.

Coakley SM and Line RF. 1988. Phytopath 78:543-550.

Daamen RA, Stubbs RW, and Stol W. 1992. Neth J Pl Path 98:301-312.

Eversmeyer MG and Burleigh JR. 1970. Phytopath 60:805-811.

Eversmeyer MG and Kramer CL. 1992. Proc 8th European and Mediterranean Cereal Rusts and Mildews Conference (Zeller FJ and Fischbeck G eds). 8­11 September, 1992. Weihestephan. Germany.

Moschini RC and Fortugno C. 1989. IV Reunión Argentina de Agrometeorología. Actas 14-17. March, 1989. Argentina.

Moschini RC and Pérez BA. 1997. IX Congreso Latinoamericano de Fitopatología. 12-17 October, 1997. Uruguay. Pg. 92.

Wheat leaf rust severity in relation to El Niño/Southern Oscillation.

R.C. Moschini and B.A. Pérez.

Leaf rust is present every year, and its importance increases as new races and conditions become favorable for its spread. The biannual leaf rust severity variation at Pergamino (Latitude: 33°56'S, Longitude: 60°33'W) were associated with the El Niño/Southern Oscillation (ENSO) phenomenon. The June­July [early] leaf rust epidemics were analyzed in relation to ENSO phases during a period of 18 years (1972 to1996, with 1988, 1991, 1992, and 1993 missing) of observed wheat leaf rust epidemics and 30 years (1967­97) of predicting the severity using the equation (PS % = 4.42 + 0.61DD12 + 0.57DRH70 ­ 30.01RI) for resistant cultivars and the equation (PS % = 2.1875 + 0.5603DD12 + 1.944DRH70) for susceptible cultivars (Mochini and Pérez 1997, 1998) developed for Pergamino. Each year was classified into one of three categories according to the Southern Oscillation Index (SOI, Troup 1965).

Equation 1 explained 88 % of severity variation, with DD12 (degree-day accumulation of base daily mean temperature (MT) > 12°C and air relative humidity (RH) > 49 %, if MT > 18°C then MT = 18°C), and DRH70 (days with RH >70 % and precipitation < 0.2 mm) being monitored from 16 August until 475 degree-days were accumulated. The resistance index (RI = 0.3) was the proportion of resistant cultivars sown each year. General linear models were fit to severity data discriminated according to cultivar infection type score, using the equation for susceptible cultivars. Deviation from the estimated value was compared to the mean 5-month SOI (Moschini and Pérez 1998), and each year was ranked and named as Niña (SOI > 75 % value), neutral + (SOI < 75 % value and > median), neutral ­ (SOI < median and > 25 % value), and Niño (SOI < 25 % value).

The El Niño years (1976, 1982, 1986, and 1994), but not 1972, were associated with an above-average observed leaf rust severity with a maximum in 1982. Considering the susceptible cultivars, the last 3 years also showed values over the median. On the other hand, La Niña years (1973 and 1975) had observed severities around or below the median. The remaining neutral years presented an erratic trend with a tendency toward values below or around the median. The analysis of estimated values for a 30-year period, indicated that 5 out of 8 El Niño years were above the median, and 3 out of 5 La Niña years resulted in values below the median. The deviation of four category ENSO classification was coincident with higher severities for El Niño years (5 and 6 out of 8 years above median for both equations) and lower for La Niña years (5 and 6 out of 8 years below median). Typical El Niño years (1982, 1991, and 1997) were associated with prominent above-average severities.

References.

Moschini RC and Pérez BA. 1997. IX. Congreso Latinoamericano de Fitopatología. 12­17 October, 1997. Uruguay. P. 92.

Moschini RC and Pérez BA. 1998. 7th ICPP. Edinburgh. United Kingdom.

Troup A. 1965. Quarterly Journal of Royal Meteorological Society. 91:490-506.

Environment-pathogen-host interaction in relationship to Puccinia recondita f. sp. tritici severity in the Chaco-Pampeana wheat region.

R.C. Moschini, V. López*, and B.A. Pérez.

*Cátedra de Estadística, Facultad de Agronomía, University of Buenos Aires, Avda San Martín 4453, (1417) Buenos Aires, Argentina.

In 1991, a group of 159 bread wheat entries were evaluated for reaction to leaf rust at Balcarce, Paraná, and Sáenz Peña, including lines, cultivars, and the South Cone Wheat Trial. Another group of 67 entries that included M. Juárez was tested separately. Thirty-nine percent ranked between R-MR and more than 40 % were MS­S. Considering the number of entries per category, a significant correlation between location and resistance (X2 = 58.8 and 22.65, P < 0.001) for both trials (n = 159 and 67 , respectively) was observed. Examining the locations by pairs (n = 159) showed that Balcarce and S. Peña were not significantly different (X2 = 1.26, P < 0.05), whereas in Paraná, cultivars from Balcarce and S. Peña were different (X2 = 35.42 and 48.91, P < 0.001).

The environmental effect was analyzed by a predictive model developed for Pergamino, with a sensitive period (16 August until 475 accumulated degree-days), and thermal accumulations of 44.8 and 66.4 (°C days of mean temperature between 12 and 18°C, relative humidity > 49 %) at Balcarce and S. Peña (Psev = 26 %), lower than those of 116.2 and 99 at Paraná and M. Juárez (Psev = 72 and 63 %).

On the other hand, Balcarce had better hydric conditions (27 days without rain, relative humidity > 70 %) compared to S. Peña (7 days). Paraná and M. Juárez had 17 and 22 days, respectively, with adequate humidity, thus explaining the high severity levels observed in 1991 associated with adequate thermal conditions.

Reference.

Moschini RC and Pérez BA. 1997. IX Congreso Latinoamericano de Fitopatología. 12­17 October, 1997. Uruguay.

Reaction of Hordeum distichum to Pyrenophora teres.

D.E. Barreto*, M.A. Carmona*, M. Ferrazini*, and B.A. Pérez.

*Facultad de Agronomía, University of Buenos Aires, Avda San Martín 4453, (1417) Buenos Aires, Argentina.

Barley, with 230,000 ha in cultivartion mainly in the Buenos Aires area, has increased because of the demand from the malting industry. Net blotch of barley caused by P. teres f. sp. teres is one of the most important diseases, and may cause yield losses of 20 to 35 % and lower brewing quality. Recent surveys between 1990 and 1994 indicated that net blotch was the prevalent disease and that 80 % of the area was planted with the highly susceptible cultivars Quilmes Alfa and Q. Pampa. Because of requirements from barley growers and the malting industry, breeding for net blotch resistance has become a priority. Several lines and cultivars have been reported with resistance to net blotch, and resistance genes have been assigned to some of them. Resistance genes were reported in Hoyo Epuyen, Rojo, and H. spontaneum in Argentina. Following described methodology, we have identified genotypes with resistance at seedling and adult plant stages to a mixture of isolates of P. teres collected in Buenos Aires. A group of 38 lines and nine cultivars from Argentina and 11 introductions from Brazil and U.S. were evaluated for resistance to net blotch. The pedigrees of selected cultivars are presented below. The Argentine materials 4130, 4142, 4173, 4176, 4179, 4181, 4195, 4199, 4202, 4203, 4218, Ana, BV 10-87, and BV 17-87; the U.S. introductions B1202, B1215, B1614, Excel, and Robust; and the Brazilian introductions B26, B27, B28, B36, B43, and MN599 were resistant at both seedling and adult growth stages.

References.

Carmona M and Barreto D. 1995. Fitopatología Brasileira 20:509-510.

Douiyssi A, Rasmusson D, and Wilcoxson R. 1996. Plant Dis 80:1269-1272.

Frecha J. 1958. Rev Investigaciones Agricolas 13:1.

Tekauz A. 1990. Can J Plant Sci 12:141-148.

Seedling resistance to an isolate of powdery mildew in F3 lines of the bread wheat cross Buck Charrua / Thatcher.

S. Zuccotty1, B.A. Pérez, E. Wright1, and V. López2.

1 Sanidad Vegetal and 2 Cátedra de Estadística, Facultad de Agronomía, Avda San Martín 4453 (1417) Buenos Aires, Argentina.

Blumeria graminis, the wheat powdery mildew pathogen, may cause yield losses of over 37 %. In Argentina, B. graminis is present during both seedling and adult stages mainly in the northeast. The Argentine bread wheat cultivar Buck Charrúa was released in 1989 by José Buck S.A. This cultivar has high resistance at the seedling stage to a B. graminis isolates avirulent on Pm2, Pm3a, Pm3b, and Pm4a, and virulent on Pm1 and in the adult plant under field conditions.

The seedling resistance to an isolate avirulent on Pm2, 3a, 3b, 4a, 4b, 5, 7, 8, 17, (1+2+9), (1+4b), (2+4b), (2+6), Arkas, Sicco, Solo, Timmo and virulent on Pm1, 3c, 6, (10+15), (11+15), and (14+15) was studied in F3 lines derived from the cross 'Buck Charrúa / Thatcher'. The grouping of 17 homozygous resistant, 43 segregating, and 14 homozygous susceptible lines (X2 = 2.189, P > 0.05) suggested the expected 1:2:1 ratio for a single dominant gene. The seedling resistance to powdery mildew in Buck Charrúa may have been derived from the winter wheat Lovrin.

Institute of Genetics - INTA - CICA.

CC 25, (1712) Castelar, Buenos Aires, Argentina.

Epidemiological studies on a wheat mutant that simulates disease resistance response.

A. Acevedo*, E. Antonelli, and M.L. Federico.

* Departamento de Ciencia y Tecnologa, UNQUI, (1876) Bernal, Buenos Aires, Argentina.

The HLP (hypersensitive-like phenotype) mutant was isolated after a mutagenic treatment performed with ethylmetane sulphonate in the Argentine bread wheat cultivar Sinvalocho M.A. (Acevedo 1996). A monogenic inheritance controls the expression of the mutated character, and the hypersensitive-like phenotype is due to two homozygous recessive alleles. The spontaneous disease resistance response becomes evident once the fifth or sixth leaf has emerged and is remarkable in leaf blades, leaf sheaths, and tissues of the spike.

Mutants simulating disease resistance response in the absence of pathogens have been reported in Arabidopsis thaliana (Dietrich et al., 1994), H. vulgare (Wolter et al. 1993), and Z. mays (Pryor 1987). However, to our knowledge, the HLP mutant is the only member of this mutant class reported so far in T. aestivum. This mutant class indicates that host factors alone are enough to produce a visible phenotype that resembles the lesions caused by pathogen attack. Significant resistance to normally virulent plant pathogens was reported in lsd (lesions simulating disease resistance response) mutants of Arabidopsis (Dietrich et al. 1994). This led us to examine whether the HLP mutation increased the tolerance to plant pathogens. To this end, inoculation studies were performed in leaf seedlings of the HLP mutant and the isogenic motherline (Table 1).

No qualitative differential response was observed when infection types in the mutant and the mother line were compared. The following observations may explain this phenomenon: 1. Although the inoculation and determination of infection types preceded the spontaneous appearance of the disease resistance response in the HLP mutant, it is likely that the mutant must already exhibit the spontaneous disease resistance response at the time of inoculation in order to be more tolerant to plant pathogens than Sinvalocho M.A. This experiment is currently in progress. 2. Even though the type of infection is qualitatively the same in seedling leaves of both stocks, it is likely that quantitative studies currently in progress will reveal differential tolerance to plant pathogens, i.e., a lower number of pustules/leaf area in the HLP mutant as compared to Sinvalocho M.A. 3. The HLP mutant identified in wheat might not be more tolerant to normally virulent plant pathogens and might differ from the lsd Arabidopsis mutants in protective roles against plant pathogens.

References.

Acevedo A. 1996. Isolation of a wheat mutant that simulates hypersensitive-like phenotype in the absence of pathogen. Ann Wheat Newslet 42:40-41.

Dietrich RA, Delaney TP, Uknes SJ, Ward ER, Ryals JA, and Dangl JL. 1994. Arabidopsis mutants simulating disease resistance response. Cell 77:565-577.

Pryor A. 1987. The origin and structure of fungal disease resistance genes. Trends Genet 3:157-161.

Wolter M, Hollricher K, Salamini F, and Schulze-Lefert P. 1993. The mlo resistance alleles to powdery mildew infection in barley trigger a developmentally controlled defence mimic phenotype. Mol Gen Genet 239:122-128.